The present invention relates to a sheet conveyance apparatus which is mounted onto an electrophotographic copying apparatus or the like, and, in particular, to a reliable sheet conveyance apparatus wherein, even rollers rollers which are transporting copying sheets during a conveyance step are driven respectively with a different speed, an excessively large force is nevertheless not exerted on a copying sheet, and a copying sheet conveyed with an askew orientation being may be easily corrected.
Conventionally, when transporting a copying sheet from a sheet feed apparatus to an apparatus such as an electrophotographic copying apparatus, the sheets fed from the sheet feed apparatus are sheet by sheet further transported to registration rollers disposed on the electrophotographic copying apparatus, thereby the registration rollers are activated at a specific timing in order to transfer the sheets.
A conventional copying sheet conveyance apparatus has the following disadvantages. During the sheet conveyance, when conveyance rollers fail to transport a copying sheet with a uniform conveyance speed, the sheet becomes slack or excessively tight. Or, if the positional relation between an image forming member and a registration roller is not set in correct position, the copying sheet may be transported askew, and if this misoriented sheet is further transported without any correction, the finally formed image will be adversely affected. In order to solve these problems, conventionally, a conveying part extending from the sheet feeding part, including the sheet cassette, to the registration part, including the registration roller, is integrally constructed to form one unit, and then the positional relation between such unit and the image forming member is adjusted to set them into the correct position. However, since the above-described unit becomes too big in size, it may be difficult to move to adjust its setting. Further, in recent years, the sheet feeding part and the sheet conveyance part of a copy machine capable of handling a great number of sheets has become large in size. Accordingly, setting such adjustment becomes more difficult.
The present invention further relates to a sheet conveyance apparatus which is not adversely affected by a fluctuating load in the main body of the electrophotographic copying apparatus. Namely, when feeding a copying sheet from a sheet feed apparatus to an apparatus such as an electrophotographic copying apparatus, the copying sheets fed from the sheet feed apparatus are transported sheet by sheet to a registration roller disposed in the electrophotographic copying apparatus or the like, wherein the registration roller is actuated at specific timing in order to further transport the sheets.
During this sheet conveyance operation, a driving force of a driving unit is used also for driving an image-carrying member on the electrophotographic copying apparatus. The driving force is transmitted to a registration clutch which actuates or stops the registration roller.
With a sheet conveyance apparatus having the abovementioned arrangement, however, the driving force for driving the registration roller is derived from the driving unit for the main body of the electrophotographic copying apparatus and is adversely affected by the fluctuation in load being exerted on the image-carrying member. Thus, the rotation of the registration roller is adversely affected. Accordingly, the line speed of the registration roller is not always constant, thereby adversely affecting the finally formed image.
Therefore, one object of the present invention is to provide a sheet conveyance apparatus, which is a unit independent of an electrophotographic copying apparatus and is arranged at the portion between the sheet feed apparatus and the imageforming portion on the electrophotographic copying apparatus, and contains the registration roller, wherein the sheet conveyance apparatus is not adversely affected by the load fluctuation of the main body of the electrophotographic copying apparatus and is free from the imaging failure in the course of an image forming operation because the sheet conveyance apparatus is provided with a driving unit, independent of the electrophotographic copying apparatus, for driving a conveyance roller and a registration roller.